Diffuse osteosclerosis in a patient with systemic mastocytosis

Osteosclerosis refers to an abnormal increase in bone density resulting from excessive bone formation and/or reduced bone resorption. We present a case of a 31-year-old woman with acute-on-chronic abdominal pain, flushing, and diarrhea. Diffuse, mottled sclerosis involving the entire axial and appendicular skeleton was incidentally identified on imaging. Diagnostic investigations for osteosclerosis revealed a raised tryptase, leading to a bone marrow and trephine analysis. This demonstrated abnormally spindle-shaped mast cells, more than 15 in a group, with positive staining for tryptase which was consistent with systemic mastocytosis (SM). In the absence of "C" findings, a diagnosis of indolent SM complicated by diffuse osteosclerosis was made. Treatment with a histamine type-2 receptor antagonist provided mild symptomatic relief. In this report, we discuss the differential causes of osteosclerosis and the pathogenesis of bone manifestations related to SM, along with subtype-specific SM treatment options.